supersnake67

Just installed an catless x pipe on my 2004 mustang gt and got code p2270 bank 1 sensor 2 stuck lean ? I swapped my MIL's and rear 02 sensors to opposite sides to see if the code would swap banks and it didnt, it comes back on about every 2 key cycles with bank 1 sensor 2 . I believe I have an exhaust leak around the manifold and down tube on passenger side I bought a new fel pro gasket and installed it with the thicker graphite side facing the manifold and after doing some reading I'm thinking I put it on backwards I do hear a slight tick when car is in the air but dont know how bad the leak has to be to set the lean code . Does anyone have any ideas or might've had a CEL come on from an exhaust leak? Sorry I tried to post in the 96-04 forum but kept re-directing me saying there was a problem . Any help would be great

jwog666

if you pulled out the cats and installed a non catted x pipe you will get codes for the downstream o2 sensors unless you install o2 simulators or use a tuner to turn the rear o2 sensors off. the downstream o2 sensors are used to make sure that the catalyst is functioning, since you removed them that is a problem.

supersnake67

I understand that , thats why I bought MIL eliminators. At one point I thought maybe one of the MIL's were bad and thats why I got the code but I switched the MIL's around so the one on the passenger side is now on the driver side and still got the lean code on the passenger side? I swapped everyting MIL's , extensions and 02 sensors to the opposite sides and still get Bank 1 Sensor2 ,which leads me to believe I'm getting air in somewhere to cause a lean code . Was just curious if I'm chasing my tail or if anyones had any wierd exhaust leak problems.

jwog666

sorry i misread about ther mil eliminators, if you think that you have a leak and it is actuall sucking in air you should also be throwing lean codes for the upstream sensors as they are in the downpipe as well.

supersnake67

Thats kinda what I was thinking but maybe the front sensor doesn't have enough time to throw a code and the rear sensor is telling on the front sensor that somethings wrong if that makes any sense . The voltage is good with the sensor and doing the swapping with the MIL's and 02's kinda leads me to the only other thing it could be is an exhaust leak ?